Physical principles are basic to an analysis of peristaltic function and sphincter competence in the gastrointestinal and genitourinary tracts. Peristalsis is produced by a coordinated muscular activity which changes luminal dimensions and pressures in a patterned way. Sphincter competence depends on tonic contracture of the spincter muscles, which is inhibited during the peristaltic sequence. An adequate knowledge of the structural and physiological characteristics of the gastrointestinal and genitourinary tracts is necessary for the evaluation of normal peristaltic function and of pathologic conditions leading to derangements in motility, obstruction and reflux. Using previously developed and available techniques we plan to study the effect of stretch, pharmacologic agents, and electrical stimulation, on in vivo and in vitro, normal and abnormal portions of the gastrointestinal and genitourinary tracts. The relationships between intraluminal pressure, length, diameter, circumferential and longitudinal forces, stress, strain and velocity of contraction will be investigated in order to define the factors which govern normal behavior, and to determine how these factors are modified in pathologic conditions. Using these modalities we will assess some mechanical and surgical procedures which alter the mechanical characteristics of the gastrointestinal and genitourinary tracts. The long term goal of these studies is to define the mechanical characteristics of the whole gastrointestinal and genitourinary tracts.